Weird behaviour with after-line-breaking and minimum-length-after-break

[Thomas Morley]

Hi,

consider the following code:

\version "2.23.1"

\paper { ragged-right = ##t }

{
  \override TrillSpanner.springs-and-rods = #ly:spanner::set-spacing-rods
  \override TrillSpanner.minimum-length-after-break = 60
  \override TrillSpanner.minimum-length = 60
  \override TrillSpanner.after-line-breaking = ##t

  b1\startTrillSpan \break b\stopTrillSpan
}

I see two bugs here:
(1)
Setting after-line-breaking = ##t should enable printing the
TrillSpanner on second line.
It does not - for every tested version, starting with 2.12.3.

(2) minimum-length-after-break takes affect on second line although
TrillSpanner is not continued there.
If minimum-length-after-break is unset, minimum-length is applied to
the not printed part of the broken TrillSpanner.
This happens even if after-line-breaking = ##f

We currently have seven grobs with after-line-breaking set to
ly:spanner::kill-zero-spanned-time:
DurationLine, Glissando, Hairpin, LyricHyphen, TrillSpanner,
VoiceFollower and VowelTransition

TrillSpanner is the only one with bug (1)
All of them suffer from bug (2)

Cheers,
  Harm

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